The Stovebolt Site Forums The Shop Area Driveline MISSING: Brake Fluid! it's a puzzler, folks...

Hey there everyone

I've been away from the 'bolt for a few weeks..."real life" very rudely intruded. I hate it when that happens.

I got my rear brakes fixed up, and driving is so much more fun now....well, it was fun before in the way a roller coaster is fun..."AIIEEEE! I MIGHT DIE!!!"

Anyhow, I have been driving my wonderful truck (53 1/2 ton) to work for a few days (it's only 4 miles, so no biggie). I come home yesterday and park in the drive like normal...the whole way home brakes work just fine. BUT when I come out to start it this morning my brake pedal goes all the way to the floor! Confused, I pull out my wrench and check the master cyl...and it's almost EMPTY. I figure one of the front cylinders must have gone out. So I go looking at the tires and under the car and find NO fluid on the ground!

WTF?

Um...where could that brake fluid be? I have the 'dog bowl' hubcaps, could it have somehow spilled out into there?

And of course i'm PO'ed because I bet I have air in the lines now. Sonofa...

Any ideas? I just ordered front cylinders and shoes will probably need to head back to the shop. It's fine though, because I love this truck so much it's starting to alarm me.

GirlDriver,

I would put my money on the master cylinder.

Typically, if it were one of the wheel cylinders, you would probably see fluid on the back of a wheel, or on the brake backing plate.

You're probably not seeing any fluid on the ground, as you're pumping it out of the master cylinder while you're moving etc.

I would venture a guess that if you looked closely at the M/C, you'll either find fluid on it, or even the bottom of the cab, where the wind has blown it up along the bottom.

Fortunately, it's not that difficult of a job to replace, and bleed the brake system.

Of course I should be talking, my 52 has been sitting in the same spot since May, because of this very reason.

Take a look at the hoses as well - especially the one that serves the rear brakes. All that leaves is the lines. Sounds like a complete system check is in order.

Hm, ok.

So if I fill the master up again, then pump the brakes a bunch, do you think the leak would show itself? Or would it only appear 'under load' so to speak?

If there is a rubber boot on the master cylinder ,look there. Sometimes fluid will accumulate in the boot before it leaks out where the brake rod goes into it.

oh..and if anyone knows...what do the master cyl repair kits that some online retailers sell repair? Just the moving parts?

You usually get the piston with seal, separate moving seal, front spring, residual valve and maybe the rubber boot. It is also nice if you get a new top filler gasket and the line fitting copper ring. I wouldn't buy anything until you see where it is leaking.

LMC has them for $13.

Remember the master needs to be bench bleed. I just did my 64 after doing all the slaves first. I should have done the master first since the increased pressure caused the master to blow fluid all over the interior and brake fluid is not nice to painted surfaces.

I know it's not OEM but I added a set of “speed bleeders” front and rear.
My goodness, what a way to turn a bleed job into a pleasurable experience.

I know it is blasphemous to suggest but in the spirit of safety I would look to upgrading the brakes somewhat. Now I'll just cover my head and turn off the fan as it all comes flying.

You can put a kit in the master cyl. but you have to hone it first. You can buy a hone for under $10 at most discount tool shops. If it is pitted or grooved too bad you will need a new one. You can fill the master cyl & pump them up & you should find the leak. It,s a good idea to do the master cyl regardless what else is done. Once you move those parts around if it didn,t leak before it will now.

lol big chevy

So you mean the disc brake conversion, like the kits you see here and there? Like you say, blasphemous, but I hear ya. Just the other day some lady in a beemer pulled out right in front of me. Foolish, seeing how it's a big chunk of steel aimed right at her fiberglass car. The brakes locked up and squealed really well. I bet she peed on her leather seat But it was hairy for a couple of seconds there.

I bet my dad is going to start in on discs brakes any day now. Mebbe I'll tell him he's welcome to do it anytime

Hey Wrenchbender, thanks for your comments--so just to be sure, when you say once you move those parts around you mean replacing the old wheel cyls? Or what? I'm sorta new at this, sorry.

Honestly the master cyl is really cruddy looking. I'm checking the prices for new ones online...I might just buy front shoes/cyls and the master cylinder and ask my mechanic for a quote on doing it all.

If you see no leaks and u are losing fluid and you have a brake booster, check the booster, it could possibly be leaking into the booster.

Sorry I,m not real good at explaining these things. These old brake cyls. get cruddy over time. The fluid breaks down & moisture eats into the cylinders. when you replace parts you move the internal rubber parts over the cruddy area. If the cyls. didn,t leak before they will soon. Anytime you replace brake shoes you should o,haul or replace the wheel cyls. Late model vehicles or old ones. Any time I get a new old vehicle The first thing I do as far as brakes go is rebuild the master cylinder.

Power brake cylinders, brake boosters, vacuum boosters or whatever you choose to call them are notorious for sucking brake fluid out of the master cylinder, they can hold a lot of it too before they start to leak it out.

Its a 53 half ton. Those dont have a brake booster. It has the master cyl. in the floor,, as she explained earlier.
Seems like there should be a friendly neighborhood 'bolter in the area that could go by and help her out??